Is the World More Urban Than We Thought?

I spend a lot of time at the beginning of my chapter on "The Urban Transition" on the ways in which "urban" is defined around the world. Indeed, we usually think of it as a dichotomy between urban and rural, whereas I suggest we really should think of it as a continuum or a gradient. One of my recent PhD students, Dr. Magdalena Benza, implemented such a measure using our data for Ghana and a paper from that research was published last year in the journal Population, Space and Place. The United Nations Population Division tends to define urban as a dichotomy based on the definitions of urban used by member nations. By those criteria the world's population is currently more than 50% urban and will be about 2/3 urban by the middle of this century.

But, wait a minute! What if those estimates by the UN are too low? Thanks to another of my former PhD students, Dr. Debbie Fugate, for linking me to an article today from Reuters discussing the European Commission's new methodology for defining urban populations based on the classification of satellite data. Now, to be sure, the headline of this piece--a quote from the European Commission researchers--is a bit dramatic: "Everything we've heard about global urbanization turns out to be wrong." That's a bit of an exaggeration, but the use of satellite imagery does give us a different perspective, as I and my colleagues have seen, and as a good friend of mine, Dr. Deborah Balk at CUNY has also been discovering for a long time.

Using a definition made possible by advances in geospatial technology that uses high-resolution satellite images to determine the number of people living in a given area, they estimate 84 percent of the world's population, or almost 6.4 billion people, live in urban areas.

"Everything we've heard about global urbanization turns out to be wrong," said lead researcher Lewis Dijkstra.

Asia and Africa, which are routinely cited as majority-rural continents that are rapidly urbanizing, turn out to be well ahead of figures in the U.N.'s latest estimates. Once thought to be about 50 percent and 40 percent urban respectively, the new research argues Asia and Africa are closer to 90 percent and 80 percent, or roughly double previous estimates.

Those percentages translate to billions of additional people living in cities and urban areas, such as towns and suburbs, than previously thought. "If this is true, the impact is going to be massive," Dijkstra said. "A lot of development aid was geared toward rural."

The reason for the past errors is simple, Dijkstra said, because countries self-report their demographic statistics to the U.N. and they use widely different standards.

So, the researchers at the EC derived their own consistent definition: 

According to the European Commission definition, any contiguous stretch with at least 50,000 people and a population density of 1,500 per square km is considered an urban center. Any area with at least 5,000 people and a population density of 300 per square km is classified an urban cluster. Rural areas are those with less than 300 people per square km.

You can appreciate, of course, that you can't actually count people from satellite images, so you're going to need census and/or survey data to go along with that. There's a lot of work involved here, and you can check out the European Commission's database here. You can also make your own comparisons with the UN data, which are found here. Keep me posted on what you find out!